Amanda &amp; Steve

Is this the ultimate in automated ‘bot Spam Killers?
Spam is the bane of WordPress admin’s lives; auto-generated Spam can bypass unset hidden fields from the WordPress comment page by directly submitting the comment to WordPress.
This plugin does two things:
<ul>
<li>Removes the ‘Comment Author URL’ field from the WordPress comments form; for most non-technical blogs this optional field is irrelevant.</li>
<li>Kills WP (hey that saves some CPU cycles) if a comment is submitted which contains a Comment Author URL.</li>
</ul>
Website spam ‘bots have two aims, firstly they populate spam links within the main body of a spam comment, and the spam ‘bot also includes the spam destination in the Comment Author URL of the comment field.
We put together this little plugin as despite running two other anti-spam plugins + Google Captcha, ‘bot spam was still getting through. This was resulting in an hour or so each week weeding out the real comments that had fallen into the spam bucket due to the real commenter failing to complete the Google Captcha correctly. We also noticed that real user comments reduced with Google Captcha in place.
We don’t need to stand for this any longer; say goodbye to Comment Author URL Spam and save CPU cycles!

TMD Spam Killer

Hides the 'Comment Website URL' field, kills WP if a spam 'bot submits a comment which includes a Comment Author URL.

webvitaly

kudlav

This is fork of successful Anti-spam plugin v5.5 written by webvitalii, for more info visit <a href="https://github.com/kudlav/anti-spam/" rel="nofollow ugc">GitHub Fork</a>. 
From version 5.6 maintained by kudlav.
<ul>
<li><a href="https://github.com/kudlav/anti-spam/" rel="nofollow ugc">GitHub</a></li>
</ul>
Anti-spam Reloaded plugin blocks 100% of automatic spam messages in comments section and also blocks all trackbacks.No captcha required.
Plugin is simple and easy to use: just install it and it just works.
Blocked comments can be stored in the Spam area and converted to regular comments if needed.
Anti-spam Reloaded plugin is GDPR compliant and does not store any other user data except of the behaviour mentioned above.
Plugin blocks spam only in comments section.. 
Plugin does not block manual spam (submitted by spammers manually via browser).
<h3>Compatibility</h3>
All modern browsers and IE11+ are supported. 
Anti-spam Reloaded plugin works with disabled JavaScript. Users with disabled JavaScript should manually fill current year before submitting the comment.
Server compatibility:
<ul>
<li>WordPress 3.3 – 6.5</li>
<li>PHP 5.6 – 8.2</li>
<li>Doesn’t use jQuery</li>
</ul>
Plugin is incompatible with:
<ul>
<li>Disqus</li>
<li>Jetpack Comments</li>
<li>AJAX Comment Form</li>
<li>bbPress</li>
</ul>
If site has caching plugin enabled and cache is not cleared or if theme does not use ‘comment_form’ action 
and there is no plugin inputs in comments form – plugin tries to add hidden fields automatically using JavaScript.
<h3>How does it work?</h3>
The blocking algorithm is based on 2 methods: ‘invisible js-captcha’ and ‘invisible input trap’ (aka honeypot technique).
<h4>‘invisible js-captcha’</h4>
The ‘invisible js-captcha’ method is based on fact that bots does not have JavaScript on their user-agents. 
Extra hidden field is added to comments form. 
It is the question about the current year. 
If the user visits site, than this field is answered automatically with JavaScript, is hidden by JavaScript and CSS and invisible for the user. 
If the spammer will fill year-field incorrectly – the comment will be blocked because it is spam.
<h4>‘invisible input trap’</h4>
The ‘invisible input trap’ method is based on fact that almost all the bots will fill inputs with name ’email’ or ‘url’. 
Extra hidden field is added to comments form. 
This field is hidden for the user and user will not fill it. 
But this field is visible for the spammer. 
If the spammer will fill this trap-field with anything – the comment will be blocked because it is spam.

TMD Spam Killer vs Anti-spam Reloaded